Approximately 25% of the world's food crops are contaminated every year with mycotoxins, creating an ongoing, serious threat to human health and food and livestock industries. Control of mycotoxins is a global challenge due to their high toxicity to animals and humans and their widespread occurrence in agricultural commodities.
Trichothecene mycotoxins represent one of the most important mycotoxin classes that comprising naturally occurring metabolites produced primarily by Fusarium but also other species of fungi (Stachybotrys, Myrothecium, and Trichothecium) on a variety of cereal grains. The mycotoxins are known to be associated with several diseases in animals and humans (Ueno, 1983; Miller and Trenholm, 1994; Pittet, 1998; D'Mello et al., 1999; Placinta et al., 1999; DeVries et al., 2002; Conkova et al., 2003; Sudakin, 2003; Eriksen and Pettersson, 2004; Desjardins, 2006). Deoxynivalenol (DON or vomitoxin) is a specific trichothecene mycotoxin which is frequently encountered in human foods. DON is associated primarily with Fusarium graminearum (Gibberella zeae) and F. culmorum, fungal pathogens causing head blight (scab) of small-grain cereals and ear rot of maize.
Annually, about 10 million hectares wheat and 1.4 million hectares maize are seeded in Canada. Accordingly, control of mycotoxin contamination has been one of the major challenges facing the cereal industry. A survey conducted in Eastern Canada during 1991 to 1998 found that maize had the highest incidence of DON contaminated samples (0.1 mg/kg and over), which was 90%, followed by wheat, 82%, and barley 73%. In 2003, DON was detected in 63% of samples obtained from cereal-based infant foods from the Canadian retail market. Many outbreaks of acute human diseases have been attributed to consumption of Fusarium-contaminated grains and, more recently, to the presence of DON at reported concentrations of 3-93 mg/kg in grain for human consumption (Canady et al., 2001).
Mycotoxin contamination of feed ingredients also has been a serious threat to livestock industry, particularly swine production. It is well known that consumption of DON-contaminated feed can cause loss of appetite, vomiting, lesions of the intestinal tract and immunosuppression in animals (Eriksen and Pettersson 2004). Weight gain of pigs can be reduced by 5 to 10% with DON levels between 1 and 2 parts per million (ppm) and may be reduced by 50% if toxin levels in consumed feed are in the order of about 5 to 10 ppm (Purdue University; OMAFRA).
The current practice to reduce or contain mycotoxin contamination is focused mainly on the prevention of contaminated grain materials from entering the food chain through regulation, detection and compliance. However, since efficient prevention of mycotoxin contamination is not always feasible or practical, various physical, chemical and biological methods have been studied for use in decontamination of grains containing trichothecenes. For example, cleaning methods, such as gravity and sieving separation, dehulling and washing procedures can reduce the concentration of DON in wheat and maize (Trenholm et al., 1992). Thermal treatments by microwave or convection (Young, 1986) also may be used. Chemical detoxification by using oxidants such as ozone and sodium bisulfite (McKenzie, et al., 1997; Young, et al. 1986), reductants such as ascorbic acid (Swanson, et al., 1984) and alkali such as sodium hydroxide (Young et al., 1986) have been investigated. However, such treatments are often expensive, time intensive, lack efficiency, or produce deleterious side effects on the food products. Further, these methods often are not amenable to large volumes of food products and are generally considered undesirable by food/feed industries and/or consumers.
A variety of approaches have been used to reduce mycotoxin effects on livestock industries. The use of adsorbents as feed additives is common. Such adsorbents may include alfalfa fibre, hydrated sodium calcium aluminosilicate (HSCAS), bentonite, special types of clay, etc. The use of grains with no or low mycotoxin contamination to dilute mycotoxin level in feed is another common approach. Unfortunately, the use of adsorbents in feeds to remove mycotoxins is not only relatively expensive, but also specific to particular mycotoxins. Some of the most popularly used adsorbents, such as hydrated sodium calcium aluminosilicate (HSCAS) and the like, are not effective against DON. Further, the dilution method to reduce mycotoxin contamination by mixing contaminated ingredients with high quality grains is difficult to implement because the degree of contamination is often not known and thus there are questions about the extent of dilution needed to reach contamination levels which would be considered acceptable. Some European countries have already banned the use of this procedure.
Despite a plethora of information regarding the biochemistry, toxicity, and modes of action of mycotoxins, there still remain no viable solutions for either pre- or post-harvest control/eradication of these toxins (Cardwell et al., 2001). In developed countries, substantial costs are incurred through testing, compliance and research to prevent entrance of mycotoxins into the food chain. In the United States these costs are estimated to be about US $500 million to $1.5 billion per year (CAST, 1989). In Canada, losses of $100 million were accrued in 1996 following a Fusarium epidemic in Ontario (Schaafsma, 2002).
Today, the livestock feed industry is facing an even greater challenge due to the increased incidence of Fusarium ear rot of corn and the competition for corn from the emerging biofuel industry. One way in which both the biofuel industry and the livestock industry have been able to make synergistic use of the limited amount of corn available, is for the livestock industry to use the by-products created from the biofuel industry as a protein source to feed animals. However, ethanol fermentation does not destroy mycotoxins, such as DON, but, in fact, concentrates the levels to be 2 to 3 times higher than the starting material, which poses a serious risk to the livestock fed these by-products.
There is a need in the art for novel products and methods for mycotoxin control and/or decontamination. Further, there is a need in the art for specific, efficient and environmentally sound ways for decontamination/detoxification of mycotoxins.